The work of architects and builders who use dimensional stone is only as good as the stone itself - and the hands that install it.
That's where Construction Testing Sciences LLC comes in. The firm can evaluate both the strength of materials used for a project as well as the methods used to install it. The newly founded firm tests dimensional stone from around the globe.
"We never know what we're going to be test-ing until it comes in the door," said general manager Jack Gary.
Once CTS receives a sample of material from a client, the basic tests takes about two weeks. The materials are rated primarily according to American Society for Testing and Materials International (ASTM) standards, although CTS is also versed in other international standards as well.
"Probably the trickiest part of product testing is fabricating test fixtures that are stronger than the items we test," Gary said. "Also, building fixtures that simulate the actual use of the prod-ucts can be challenging."
The heart of the nearly 3,000 square-foot CTS lab is a universal test machine - a Tinius-Olsen 120,000 lb. Super L retrofitted with state-of-the-art programmable computer operated controls. Using it and other lab facilities, CTS runs a gamut of tests that include rating the structure, compression and flexural strengths of construction materials, determining absorption characteristics and testing their responses to extremes of heat and cold. The resulting infor-mation is provided to project engineers to help them determine the best way to install the stone.
After many years in the business, Gary has determined that the most common flaw in dimensional stone is not the material itself. "It's more in workmanship than in the product itself -it's human error."
Based in Garland, Texas, CTS has only been in business for three months, but Gary has been in the business for much longer. "I've been in the lab business for almost 30 years and am try-ing to start out on my own and see what hap-pens. I've been in the construction business and materials testing business since 1981."
Gary is general manager, vice president, part-owner and "chief bottle washer" of CTS. The president of the company is Ian Venegas.
Generally, CTS tests marble, limestone, gran-ite, travertine, and other common dimensional stone. The most exotic material that Gary has tested is porphyry, an igneous rock formed from magma. It was especially prized for decoration in Imperial Rome, where it was used in columns, altars, fountains and other items.
"It's actually volcanic material," he said. "Surprisingly, it is one of the hardest materials I've ever tested. People think of lava rock being so porous, but porphyry is best compared to a granite as far as hardness."
CTS is testing two different types of granite and a white marble that are being used in inte-rior and exterior work on 4 World Trade Center, which will face directly onto the World Trade Center Memorial Park in Manhattan. The 72-story tower is replacing Four World Trade Center, a nine-story office building that was damaged beyond repair during the Sept. 11, 2001, terrorist attacks by Al-Qaeda. The origi-nal building was crushed by debris when the south tower of the World Trade Center fell. Out of all the materials that Gary has tested over the years, it is marble and sandstone that pose the most challenges for builders because of physical flaws.
"Marble, if it's used in certain applications, has a tendency to bow or curl or warp," Gary said. "We just finished doing some very exten-sive testing on marble for a high profile project in South Korea, where large slabs of marble are going to be used in a paver application. We were doing bow testing to determine what thickness of marble they would need to use for it not to bow or curl since it's being used in a flat application."
Bowing is a problem especially seen in newly constructed buildings where the facades are constructed of very thin marble slabs.
CTS also tested the marble for its response to the natural frost/thaw cycle. "Thermal cycling is what does the most damage to natural stone, marble in particular," Gary said. "In South Korea, it's subjected to extreme environmental conditions of both heat and cold."
Above: Abrasion resistance (Taber Method) on Noir des Alpes Marble. Inset: Anchor prep with T31 machine (purchased from Braxton-Bragg at StonExpo). Below, Top: Jack Gary and crew test the lifting bolts and anchors to be used on a large-scale Carrara marble scultpture at Ave Maria University in Florida.
Anchor bolts will be used to fasten panels into place and then secure the scultpture to the Oratory building structure. Bottom: NT 499 (bow test, European Method) on Oira di Creolodossola Granite.
According to a paper by Josef Ondrasina, published by the Geological Society of London, the freeze/thaw cycle damages marble and other stone "by progressive microfracturing or the loss of cohesion along grain boundaries due to the crystallization pressure of ice growth."
The CTS lab is equipped with both walk-in freezers and an industrial oven for thermal testing - artificially accelerating the weathering process by exposing the materials to extreme cold and heat.
Weak points in sandstone occur because of its layered composition, Gary said. "It can create a weak zone so they have to be very careful how it's cut out of the quarry and also how it's prepared and installed."
Gary also engages in forensic testing of materials for use by parties involved in lawsuits.
"I did some testing for a project that was for litigation purposes. It happened to be on some sandstone. There were panels falling off a building because of the way the stone had been cut and the way it was installed on the building."
Forensic investigations involve a careful recreation of the conditions of the material failure. "We build mock-ups to more or less recreate entire systems to see what part of the system is failing or to determine why it is failing," Gary said.
CTS has been doing flexural testing for stone being used in the brand new George W. Bush Presidential Center in Dallas.
The tests, performed according to ASTM standards, provide data about how stone panels will behave when they are subjected to loads either perpendicular or parallel to their bedding planes.
The George W. Bush Presidential Center is being constructed on a 23-acre lot on the campus of Southern Methodist University in Dallas, Texas. It will include a presidential library, archives and museum.
Flexural strength tests are important when stone panels are being installed inside or outside buildings. Usually, the panels are mounted independently and are only subjected to the weight of the panel itself, but design preferences can sometimes force builders to place the panels in weaker configurations.
"(The strength of the panels) may be jeopardized when an architect or building owner has a certain appearance they desire especially when the veining in the stone is very visible," Gary said.
To ensure good testing results, Gary uses several benchmarks: 1) Obtaining an estimated load at which the product should fail; 2) Making sure the product failed as anticipated and not as a result of the test methodology or fixtures; and 3) Having a sufficient quantity of samples for further testing if questionable results are produced.
It's not just stone that CTS tests. From theater and stadium seating to trailer hitches, Gary said his company is willing to test just about any component. The lab is engaged in testing landing gear components for the U.S. military's F-35 Joint Strike Fighter, which is currently under development.
According to news reports, the Defense Department plans to field the aircraft in 2016. Variations being developed include an Air Force version, an aircraft carrier-suitable version for the Navy and a vertical landing version for the Marine Corps.
Whether helping firms determine the best material to use in projects before the first panel is laid or looking into failures after the fact, CTS strives to aid architects and builders in creating the best designs possible.
For more information, please visit www.ctsciences.com or contact Jack Gary at 214-703-8911.
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